/**   
 * @Title: RSAUtil.java 
 * @Package framework.core.util.sec 
 * @Description: TODO(用一句话描述该文件做什么) 
 * @author Ching Wang  
 * @date 2013-6-13 下午3:12:08 
 * @version V1.0   
 */
package framework.core.util.sec;

import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.AlgorithmParameterSpec;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;

/** 
 * @ClassName: RSAUtil 
 * @Description: 通过AES算法对文本进行加密解密
 * @author: Ching Wang
 * @date 2013-6-13 下午3:12:08 
 *  
 */
public class AESUtil {
	private static byte[] keyValue = new byte[] {		//用户密钥
		22,25,-35,-45,25,98,-55,-45,10,35,-45,25,
		26,-95,25,-65,-78,-99,85,45,-62,10,-0,11,
		-35,48,-98,65,-32,14,-78,25,36,-56,-45,-45,
		12,15,-35,-75,15,-14,62,-25,33,-45,55,68,-88
	};
	private static byte[] iv = new byte[] {				//算法参数
    	-12,35,-25,65,45,-87,95,-22,-15,45,55,-66,32,5-4,84,55
    };
    private static SecretKey key;    					//加密密钥
    private static AlgorithmParameterSpec paramSpec;    //算法参数
    private static Cipher ecipher;    					//加密算法
    
    static{    	
        KeyGenerator kgen;
		try {
			//为指定算法生成一个密钥生成器对象。
			kgen = KeyGenerator.getInstance("AES");
			//使用用户提供的随机源初始化此密钥生成器，使其具有确定的密钥长度。
			kgen.init(128, new SecureRandom(keyValue));
			//使用KeyGenerator生成（对称）密钥。
			key = kgen.generateKey();
			//使用iv中的字节作为IV来构造一个 算法参数。
			paramSpec = new IvParameterSpec(iv);
			//生成一个实现指定转换的 Cipher 对象
			ecipher = Cipher.getInstance("AES/CBC/PKCS5Padding");    	
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		} catch (NoSuchPaddingException e) {
			e.printStackTrace();
		}
    }

    /**
     * 加密，使用指定数据源生成密钥，使用用户数据作为算法参数进行AES加密
     * @param msg 加密的数据
     * @return
     */
    public static String encrypt(String msg) {
        String str = "";
        try {        	
            //用密钥和一组算法参数初始化此 cipher
            ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
            //加密并转换成16进制字符串
            str = asHex(ecipher.doFinal(msg.getBytes()));
        } catch (BadPaddingException e) {
            e.printStackTrace();
        } catch (InvalidKeyException e) {
            e.printStackTrace();
        } catch (InvalidAlgorithmParameterException e) {
            e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
            e.printStackTrace();
        }
        return str;
    }
    
    /**
     * 解密，对生成的16进制的字符串进行解密
     * @param value 解密的数据
     * @return
     */
    public static String decrypt(String value) {
        try {
        	ecipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
            return new String(ecipher.doFinal(asBin(value)));
        } catch (BadPaddingException e) {
            e.printStackTrace();
        } catch (InvalidKeyException e) {
            e.printStackTrace();
        } catch (InvalidAlgorithmParameterException e) {
            e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
            e.printStackTrace();
        }
        return "";
    }

    /**
     * 将字节数组转换成16进制字符串
     * @param buf
     * @return
     */
    private static String asHex(byte buf[]) {
        StringBuffer strbuf = new StringBuffer(buf.length * 2);
        int i;
        for (i = 0; i < buf.length; i++) {
            if (((int) buf[i] & 0xff) < 0x10)//小于十前面补零
                strbuf.append("0");
            strbuf.append(Long.toString((int) buf[i] & 0xff, 16));
        }
        return strbuf.toString();
    }

    /**
     * 将16进制字符串转换成字节数组
     * @param src
     * @return
     */
    private static byte[] asBin(String src) {
        if (src.length() < 1)
            return null;
        byte[] encrypted = new byte[src.length() / 2];
        for (int i = 0; i < src.length() / 2; i++) {
            int high = Integer.parseInt(src.substring(i * 2, i * 2 + 1), 16);//取高位字节
            int low = Integer.parseInt(src.substring(i * 2 + 1, i * 2 + 2), 16);//取低位字节
            encrypted[i] = (byte) (high * 16 + low);
        }
        return encrypted;
    }
    
    public static void main(String args[]){
    	String str = "sa";
    	String aesStr = AESUtil.encrypt(str);
    	System.out.println(aesStr);
    	String desStr = AESUtil.decrypt(aesStr);
    	System.out.println(desStr);
    }
}
